diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
index 8b54a9ab04..5d184f20a4 100644
--- a/libavformat/mvdec.c
+++ b/libavformat/mvdec.c
@@ -381,7 +381,7 @@ static int mv_read_header(AVFormatContext *avctx)
             avio_skip(pb, 8);
             av_add_index_entry(ast, pos, timestamp, asize, 0, AVINDEX_KEYFRAME);
             av_add_index_entry(vst, pos + asize, i, vsize, 0, AVINDEX_KEYFRAME);
-            timestamp += asize / (ast->codecpar->channels * bytes_per_sample);
+            timestamp += asize / (ast->codecpar->channels * (uint64_t)bytes_per_sample);
         }
     } else if (!version && avio_rb16(pb) == 3) {
         avio_skip(pb, 4);